Run scheduler containers in cloudron network as well

This results in:
  box:scheduler Unhandled error:  { Error: (HTTP code 409) unexpected - Conflicting options: dns and the network mode

Part of #307

src/docker.js

@@ -202,7 +202,7 @@ function createSubcontainer(app, name, cmd, options, callback) {
                 },
                 CpuShares: 512, // relative to 1024 for system processes
                 VolumesFrom: isAppContainer ? null : [ app.containerId + ":rw" ],
-                NetworkMode: isAppContainer ? 'cloudron' : ('container:' + app.containerId), // share network namespace with parent
+                NetworkMode: 'cloudron',
                 Dns: ['172.18.0.1'], // use internal dns
                 DnsSearch: ['.'], // use internal dns
                 SecurityOpt: enableSecurityOpt ? [ "apparmor=docker-cloudron-app" ] : null // profile available only on cloudron